182 ALASKAN GLACIER STUDIES
advance of 114 feet, one of 183 feet, and the remarkable case of the Vernagt-Ferner whose advance attained as many as 150, 240, and 450 feet in a year. In contrast with this the Haenke Glacier in Alaska advanced over 4000 feet in a little less than ten months and the Hidden Glacier over 10,000 feet in a brief interval, probably less than a year and possibly in only a few months. The glaciers in Europe sometimes continue to advance for fifteen or twenty years when once an advance starts, the cycle from maximum to nm'TmniiTn being 85 to 50 years, contrasting with the Alaskan glaciers under discussion whose advances have lasted less than a yeac.
The case of glacier advance most nearly analogous to that of the Yakutat Bay region, of which we have found record, is that of the two small Tyrolese glaciers—the Vernagt and Ferner, which are known to have undergone great advance in 1599, 1680, 1773, 1820,1845 and 1898-1900. Some of these advances have been very great, and by their effect in damming up a tributary valley and forming a lake, whose sudden drainage has caused great floods in a populated valley have attracted attention and invited study even in early times. Reference to these earlier studies will be found in the remarkable monograph by Finsterwalder1; in which the cause for the variation in the Vernagt and Ferner Glaciers is discussed. The notable advance of the Vernagt Glacier and the less marked advance of the Ferner Glacier in 1898-1900 are described by Bltimcke and Hess; and they have also published some of the results of careful studies of these glaciers upon which they have been engaged for many years.2
In the last advance of the Vernagt glacier a swelling was at first observed in the reservoir, and later a transformation of the ice tongue followed, converting it from practically uncrevassed to crevassed condition, and causing an advance of the end. Earlier advances had been similar, though some of them were far more pronounced. There is therefore a noteworthy resemblance between the behavior of the Vernagt-Ferner and the advancing Yakutat Bay glaciers, though the 1898-1900 advance was much less spectacular and less rapid than those of the Yakutat Bay glaciers, and there is also a difference in the cause, for the Vernagt, and less notably the Ferner, is a small ice tongue fed from a very large reservoir, and the advance is ascribed to the concentrated influence of an increase in the snowfall in the reservoir, not to the effect of earthquake shaking.
From the researches of Finsterwalder, Bltimcke and Hess it seems evident that excessive accumulation of snow in the reservoir ultimately starts a wave which, gathering force, finally sweeps with rapidity through the glaciers and finds response even in the lower portions of the glaciers by rapid motion, thickening, and advance. Their important detailed work, which, in the nature of the case, could not possibly have been undertaken in the Alaskan glaciers, throws a flood of light upon the problems of ad-
i Finsterwalder, 8., Der Vernagt-Ferner, Wissenschaftliche ErgUnzungshefte zur Zeitschiift des D. u. 0. Alpenvereina, I Bond. 1 Heft. Graz, 1897; with addendum by Bltimcke, A. and Hess, H. on Die Nachmes-sungen am Vernagt-Ferner in den Jahren 1891, 1893 and 1895.
» Bltimcke, A. and Hess, H., Beobachtungen an den Gletschern des Rosenthales. Mittheflungen des D. u. 0. Alpenvereins, 1900, Nr. 4, 6 pp.; Einiges liber den Vernagt-Ferner, ibid. 1902, Nr. 18; Tiefbohrungen auf dem Hinterreisferner, 1902, ibid. Nr, 21, 7 pp.; Tiefbohrungen am Hintereisferner im Sommer, 1908, Zeitschrift fur Gletscherkunde, Band m, 1909, pp. 232-286; Tiefbohrungen an Hmtereisgletscher, 1909, ibid. Band IV, 1909, pp. 66-70; Hess, H. Zur Mechamk der GletachervorstOsse, Petermanns Geogr. Mitteilungen, 1902, Heft. V; Probleme der Gletscherkunde, Zeitschrift fur Gletscherkunde, Band I, 1906, pp. 241-254; Die Gletscher, Braunschweig, 1904. pp. 296, etc.